INTRACELLULAR ACIDITY IN VALONIA. 



By W. J. CROZIER. 



{Contributions from the Bermuda Biological Station for Research, No. 105, and from 

 the Physiological Laboratory, College of Medicine, University of Illinois.) 



(Received for publication, April 28, 1919.) 



The very large cells of the marine green alga Valonia macro physa 

 permit one to obtain several cubic centimeters of fluid from the 

 central vacuole of a single cell (cf. Wodehouse, 1917), without in- 

 volving appreciable alteration in the composition of the cell-sap 

 through protoplasmic injury during the process of extraction (cf. 

 Chambers, 1917). Estimations have been made of the acidity of this 

 cell-sap. These measurements, although perhaps revealing no 

 essentially new points of theoretic interest, are nevertheless valuable, 

 since they bear so directly upon some questions regarding the reaction 

 of the cell interior. 



The cell-sap of Valonia is much more acid than the sea water in 

 which the plant is living. The reaction of the sap from fifty cells as 

 obtained immediately after their removal from the sea was found to 

 vary in individual cases from pH 5.0 to 6.7, the mode being at 6.0, 

 the average 5.9. In thus possessing an acid internal medium the 

 Valonia cells resemble those of some flowering plants containing 

 natural indicators (Haas, 1916). 



Valonia grows in great masses at a depth of several feet beneath 

 low-water level in certain mangrove *' creeks," and also, less abun- 

 dantly, among other seaweeds, on the reefs. The alkahnity of the 

 sea water in the tidal creeks depends upon the state of the tide : at 

 flood-tide, for example, in Fairyland Creek, the water most dis- 

 tant from the mouth of the creek was at pH = 8.2, while that half 

 way toward the mouth of the creek was at 8.1, and in the adjacent 

 regions of Great Sound, 8.07; at low-tide next morning, the alkalinity 



c;;. at the head of the creek was pH = 8.3. A similar rhythmic altera- 



cn 581 



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